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The molecular structure of 1-hetero-2,5-cyclohexadiene-1-oxide, X0 , are studied and compared with their corresponding deoxygenated compounds, 1-hetero-2,5-cyclohexadiene, X, using B3L YP/6311 ++G** level of theory. Isodesmic reactions are carried out for determining the stability of X0 and X. Isodesmic reactions indicate that the compounds with X are more stable than Xo. For X0 and X, the stability is generally decreased from second row to fourth row elements of the table. Nuclear independent chemical shifts, NICS, calculations are done for investigation of homo-aromatic character ofX0 and X. For X compounds, the NICS (+0.5) as well as aromatic character are increased from 0 to Se while NICS (+0.5) for Pis highest respect to As and N.